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Discussion Starter · #1 ·
258 with BBD --the 3 vacuum solenoids which sit on top of the valve cover are receiving strong manifold vacuum . First is the Downstream Pulse Air Solenoid ( closest to the battery ) , in the middle is the Upstream Pulse Air Solenoid , finally ,closest to the carb is the Idle Solenoid which feeds vacuum to the vacuum portion of the Sol-Vac . All three solenoids have corresponding "inlet vacuum receiving ports " and "outlet vacuum delivery/passthrough/feeding ports" . Mine was setup so that the 3 short towers would be the side to receive direct manifold vacuum ; the 3 TALL towers appeared to merely pass any vacuum along to the pulse air valves or the sol-vac . Ques: Was this setup correct ?
Next , when the 3 short towers were tested for tjeir individual vacuum holding ability while no juice was applied to its corresponding solenoid , all 3 short towers held vacuum . That is , it appeared that vacuum was blocked from appearing at the TALL towers while no juice was applied to the solenoid. Question : Is that the correct setup and functionality ? Next , vacuum was individually applied to each of the TALL towers while the solenoids still lacked 12 volts of juice . All 3 TALL towers behaved the same - no vacuum held , air was let in . Question : Is that correct functionality ? The same procedure was repeated while applying 12 volts juice to each of the 3 solenoids individually and the vacuum holding ability was tested for each once more. To my disbelief , there was no change to be noted. All 3 solenoids /tower systems behaved the same as before . Question : What is happening ? I expected the solenoid plunger to move within each solenoid and alter the vacuum holding ability . My gut reaction is that all 3 solenoids are shot -- , but that seemed to be too much to occur . Can anyone shed light on this issue?

 
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Discussion Starter · #2 ·
I really haven't heard about anyone going this indepth into those 3 almost pointless vacuum solenoinds. They really don't help out the engine that much if at all. And if so, they are definately not noticeable. Check out this site: http://www.off-road.com/jeep/tech/258bbd/index.htm It should tell you just about anything you need to know about the 258.

Tim

'88 YJ, 4.2L w/Weber 32/36, Procomp 4" w/33 BFG M/T's, TFI upgrade, Stock auto tranny and everything else.
I love bein' a Jeeper!!!
 

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Excellent link from Jeepin_Tim, but I have to disagree slightly with his previous post. These solenoids DO affect the performance of the engine if they aren't functioning properly, assuming all of your emissions equipment is intact in the original setup. Without any vacuum to the pulse air control valves, the check valves will not function properly, same goes for the idle solenoid.

To answer one of your questions, yes the short towers should receive manifold vacuum while the tall towers should act to distribute that vacuum appropriately. Your other question is a bit harder, I may need some help myself on that one. First off with no juice, the tall towers should release when you apply vacuum, which is what happened in your case. They are designed to pull vacuum, so it makes sense that they didn't hold. It also makes sense that with no juice the short towers held vacuum, they should until the computer tells them to distribute that vacuum to the individual components (open).

Now, it's a mystery to me why these solenoids didn't open when you applied juice to them. They could all be shot, I don't think that's too far-fetched.

Maybe a more wise Jeeper can tell us how the computer controls the electrical side of the equation.


TEXAS1AL

84 CJ-7; 258 I6; Restored-to-Stock Condition
 
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Discussion Starter · #4 ·
Thank you both for commenting . The 258 Primer website was my starting point and it is truly an excellent site for me. It did not provide enough detail to assist me in this particular matter. Texas , you have been able to alleviate my concern as to correct routing of the vacuum supply hose from manifold vac to the 3 short towers . That is a start. Here is another piece of the puzzle , one that leads me to believe that all 3 solenoids are coincidentally shot : when the 12 volts are applied to energize each solenoid individually, I do not hear/ feel the inner plunger moving . Additionally , when I test each pair of exposed solenoid terminals with a continuity tester, the circuit is Open . Hence , I suspect that each solenoid is non-functional . I would like to learn more or else get confirmation that functioning solenoids on other Jeeps have a closed circuit between each of trhe 3 pairs of exposed terminals on the solenoid assembly.

 

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If I get time this weekend, I'll try to test my solenoids to confirm that it should be a closed circuit. This whole discussion has got me wondering if my solenoids are functioning, but I suspect they are because I can see and feel the pulse air system working with the air cleaner open and I just replaced one of my control valves. So at least I know that vacuum is getting farther down the line than in your rig.

I'll let you know when I get around to it.

TEXAS1AL

84 CJ-7; 258 I6; Restored-to-Stock Condition
 
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Discussion Starter · #6 ·
I would very much appreciate hearing of your results on the solenoid "open circuit vs. closed circuit" test. I suspect that all 3 solenoids should be their own self contained closed circuit . That is the only way I could understand that the inner core plunger of the solenoid would feel an induced magnetic field once 12 volts were applied ; thus, the plunger would be caused to move . Without the closed circuit pathway , I fail to see what would cause the plunger to move . This is all speculation on my part.

 
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Discussion Starter · #7 ·
I'm trying to figure out now what you two are trying to figure out...Why does it matter if those solenoids work? What do they do for you to help? When I had the Carter, I would disconnect those to pass emissions. Now, they are pointless for me because I have the Weber 32/36. They are useless emission control solenoids that hardly even help the sol-vac so why bother? If you are going for a better running engine, check this other link out:http://www.off-road.com/jeep/jnutter1.htm This helped out my engine a lot and so did many other cheap tricks on this board. Look around and do some research about the 4.2 and components. There is tons of info from upgrading to different ignitions to swapping in a 4.0L head.

Tim

'88 YJ, 4.2L w/Weber 32/36, Procomp 4" w/33 BFG M/T's, TFI upgrade, Stock auto tranny and everything else.
I love bein' a Jeeper!!!
 

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Jeepin_Tim,

I had the exact opposite experience as you. My Jeep failed emissions testing the first time I got it and the examiner thought it was probably the cat. I took the Jeep home and completely re-plumbed the engine, including hooking up all the solenoids (which were disconnected). After doing this, I noticed that the pulse air tubes were working and I passed the next day with no more than $10 spent on vacuum hoses. As we all know, though, emissions tests are shaky at best and who knows if it should have failed in the first place. My gut tells me, though, that those pulse air tubes helped me pass the second time.

Anyway, you're right, it's no biggy, but keep in mind that there are men out there who treat the care of a classic Jeep just as they would an antique sports car...they want everything the way it should be. Hell, when you've decided not to build your rig up, what else is there to do!

TEXAS1AL

84 CJ-7; 258 I6; Restored-to-Stock Condition
 
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Discussion Starter · #9 ·
I've always been curious about figuring those three solenoids out...and also that vacuum canister and testing to make sure that it is working correctly...

Maybe another test stilllearning could do is to watch the sol-vac switch on the side of the carb at startup...the vacuum should pass through the system and hold the carb sol-vac fully extended for 15 seconds until the solenoid on mounted on the valve cover stops the vacuum...(I think I have that right)...that would indicate whether or not that one solenoid of the three is working...

 
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Discussion Starter · #10 ·
Only when I applied either direct manifold vacuum via a bypass system or applied vacuum via a hand pump did I see the vacuum portion of the Sol- Vac become active and extend . It appeared that manifold vacuum was not reaching the Sol-Vac when the manifold vac followed the OEM route of passing through the three vacuum unit solenoid assemblies . I plan to replace all 3 solenoid units . In response to your comment re: the sol-vac activity at startup , I believe that the electrical circuit of the sol-vac ( under MCU control) is independently involved at startup and that the vacuum passage as controlled by the Idle Solenoid on the "3 vacuum solenoid assembly tree" does not impact the sol-vac 's plunger at startup. That is my understanding up to this point. Please correct me if I am mistaken.

 
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Discussion Starter · #11 ·
I got the startup info from the ORC Tech page http://www.off-road.com/jeep/tech/258bbd/solvac.htm...supposedly the mcu puts the vacuum portion on the carb sol-vac for a short time then switches it over to the electric portion for a little bit longer before turning both off...take a look at the tech page as it explains the test a little bit better then I do...

the whole vacuum system and all of its reletad inter-workings seems like it is a real neat system when everything is working correctly...its just getting there that can be a little frustrating...
 
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Discussion Starter · #12 ·
Good catch , BugSheriff. I will followup on your suggestion . As long as I was in so deep to this area, I spent hours pouring over Diagnstic Connector One and Two next to the battery . That will be another topic in the future. I appreciate your input.

 

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Stillearning6,

Just to wrap things up from my end...I know we've beaten this to death. I tested the solenoids on my rig and each one is as a closed circuit. So since your's are not closed that may be your problem.

TEXAS1AL

84 CJ-7; 258 I6; Restored-to-Stock Condition
 
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